This invention relates generally to a controller for an electrically driven compressor and more particularly to a compressor controller for monitoring various compressor operating parameters and controlling the power supplied to the compressor.
Several known compressor control apparatus are configured for monitoring the lubrication pressure of a compressor and de-energizing the compressor in the event that a condition of low pressure is detected. Such low pressure detection devices usually take the form of a relay or switch which immediately shuts off power to the compressor when a condition arises such as the lubrication pressure being below a predetermined level. Other compressor protective devices include separate equipment for protecting the compressor against short cycle operation, protecting the compressor from overloads and protecting the compressor from accelerated wear in the event that the compressor lubricating oil system malfunctions.
While these prior art devices have heretofore been satisfactory for compressor control, they have failed to appreciate the advantages of providing an integrated compressor controller which is responsive to a plurality of operating parameters of the compressor. In particular, the prior art fails to provide a time period for allowing the lubrication pressure to develop to the proper level. Many of the prior art systems are plagued with excessive compressor stoppages due to initially inadequate lubrication pressure without allowing the system to establish the proper pressure in a running state. Further, the conventional systems do not provide an alarm should the lubrication pressure be insufficient for longer than a predetermined time limit. Additionally. the prior art has failed to appreciate a controller which is configured in accordance with the above-mentioned features and to further include a timing delay circuit to prevent short cycling as well as self-diagnostic functions.